This study aims to investigate the effect of PEMF on synovial efferocytosis in anterior cruciate ligament transection (ACLT)-induced osteoarthritis in rats and to elucidate its underlying molecular mechanisms.
Male Sprague-Dawley rats (6 weeks old) were divided into three groups: ACLT group, PEMF intervention group, and sham surgery group, with 10 rats in each group. Both the ACLT group and the PEMF group underwent ACL transection to establish an osteoarthritis model, while the sham group received the same surgical procedures except for ACL transection. One week post-surgery, the PEMF group received an intervention of 3.82 mT, 10 Hz, and 1800 pulses, administered 5 days per week for 4 and 12 weeks. After the intervention, synovial tissue samples from the knee joints of all three groups were collected. Enzyme-linked immunosorbent assay (ELISA) was performed to measure the degree of inflammation. Immunofluorescence staining was used to evaluate efferocytosis activity. Quantitative reverse transcription polymerase chain reaction (qRT-PCR), Western blotting, and immunohistochemical staining were employed to detect the expression levels of MFGE8 and KLF9.
In rats with ACLT, synovial tissue levels of IL-1β and TNF-α were significantly elevated compared to the sham group (p0.001). qRT-PCR results confirmed that the mRNA expression of MFGE8 and KLF9 was significantly lower in the ACLT group compared to the sham group (p0.01), which was further corroborated by Western blot showing downregulated protein expression. Following PEMF intervention, IL-1β and TNF-α levels were significantly reduced compared to the ACLT group (p0.001). The mRNA expression levels of MFGE8 and KLF9 were higher in the PEMF group than in the ACLT group (p0.01), and protein expression was also upregulated. Immunofluorescence and immunohistochemical staining revealed reduced expression of MERTK, MFGE8, and KLF9 in the ACLT group, indicating impaired efferocytosis. PEMF intervention reversed this impairment.
PEMF intervention promotes synovial efferocytosis in ACLT-induced osteoarthritis in rats by upregulating the expression of KLF9 and MFGE8, thereby mitigating synovial inflammation in the knee joint.
The Osteoarthritis Research Society International (OARSI) recommends providing “multidisciplinary, non-pharmacological interventions focused on reducing physical disability and impairment.” As a safe and non-invasive physical therapy, pulsed electromagnetic fields (PEMF) have been shown to alleviate pain and promote functional recovery in osteoarthritis. However, the specific mechanisms underlying its effects remain unclear. This study elucidates the molecular mechanisms by which PEMF exerts therapeutic effects on knee osteoarthritis, providing a theoretical foundation for its clinical application and broader adoption.
osteoarthritis
efferocytosis
